Well, to put it in perspective, a standard uni semester is 12 weeks of content delivery. So, when you say 'a few weeks', that could translate to learning a quarter or a third of the unit curriculum ahead of the lectures, which themselves are pretty content-packed and which go a lot faster than VCE does. So, it's definitely a very challenging undertaking, even for the high-achievers.
Will it get you through uni? Is it pointless? Well, only those who have tried it can really say what it's like, and even then, it's your uni experience that matters here. There are students who use lectures as a supplementary resource to learning the content themselves via books and papers. There are students who like to annotate the provided lecture notes; others will write their own; others will use listening as their best aid to understanding. Some students will prefer being first exposed to content from a lecturer, because they find it's clearer for them than partly understanding things on their own. Others find forming peer study groups the best way to learn from each other. The point I'm trying to make is that a big part of the academic aspect at uni is finding what works for you (which can vary between different subjects, and even week-to-week!). So, it *can* work for you, and if it does, it certainly isn't pointless!
However, I'm reasonably confident it isn't necessary (and I am sure many uni students will attest to this). If you do adopt this approach, I'd like to offer a couple of comments:
If you successfully learn content (and understand it well) before it is covered in lectures, please do not underestimate the importance of the information given in lectures (and pracs, tutorials etc.). If a lecturer focuses on something, it is often prudent to give it extra attention. An example that a lecturer uses may be one among many you encounter in your own readings - but do not be surprised if an assessment question expects good knowledge of the example.
Also, if you find that you are really struggling to keep up with such a pace, please don't be too hard on yourself. Being up-to-date at uni already puts you in good stead to achieve good results. There tend to be two or three weeks during semester when assessments pile up, and it's normal for students to devote more time to assessments rather than content learning in those time periods. Try not to get too down if you need to catch up on lectures or if you need to 'cram'. If you really feel overwhelmed, there are support services available!
University can take some time for you to 'find yourself', so to speak. But usually, those who are able to figure out what works for them do well and get a great deal out of all aspects of uni life. All the best for your journey ahead!